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M.v G. FARMER.

TELEPHONIGTRANSMITTER. No. 378,298. Patented Feb. 21, 1888.

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' made in accordance with my invention.

llnrrnn STATES" MOSES G. FARMER,

PATENT tries,

OF ELIOT, MAINE.

. TELEPHONIC TRANSMITTER.

SPECIFICATION forming part of Letters Patent no. 378,298, dated February 21, 1888.

Application filed November '2, 1887. Serial No. 254,058. (No model.)

To all whom it may concern:

Be it known that I, Mosns G. FnnMnn, a citizen of the United States, residing at Eliot, in the county of York and State of Maine, have invented certain new and useful Improvements in Telephonic Transmitters, of which the following is a specification, reference being had to the drawings accompanying and forming a part of the same.

The subject of this invention is a telephonic transmittercapable of reproducing articulate speech or other sounds, particularly loud sounds, more distinctly and audibly than the ordinary transmitters heretofore used.

The instrument belongs properly to that class of transmitters known as long-distance telephones but its peculiar capabilites of reproducing articulate speech with great clearness and distinctncss make it a generally use ful'and valuable instrument.

The main object which I have sought in the construction of the device is to maintain a pernanent though yielding electrical connection or-bridgo between the two sides or terminals of the instrument and through one of the electrodes, but independent or the normally-existing path formed bythe contact of the two main electrodes. For this purpose, aside from other improvements in the details of construction to be hereinafter set forth, I support a small plumbago point by a light spring so that it remains in contact with the surface of the vibrating carbon electrode. The range of movement of this carbon electrode is limited, and the spring supporting the plumbago point is so bout that the point is constantly held in contact with the electrode by spring-pressure. It results from this that, while the carbon may be thrown out of actual contact with its up posing metallic point or electrode by sudden or extended vibrations of the diaphragm, the jarring and sputtering sounds produced by ordinary transmitters will not occur, for the great difference in the mass or inertia of the carbon button and the spring-supported point liecps them constantly in contact and prevents an actual break in the circuit.

Figure 1 is a plan view of an instrument Fig. 2 is a side view'of the same with a portion of the supporting base or plate cut away. Fig.

3 is a side view of a modified form of the invention with the base in section.

The operative parts of the instrument are conveniently mounted on the base A, through which is a perforation, R. The diaphragm (a sheet or plate, D, of iron, mica, aluminum, or the like) is secured to plate A over this opening. Above this diaphragm two standards, B B, are secured to the base to support a horizontal shaft, L. To said shaft is secured the rigid arm V, carrying at its extremity the cup 0, containing the carbon electrode or button it, which in its normal position rests lightly upon the platinum point 0, attached to the diaphragm D. An arm, P, is also secured to the shaft L by a sleeve and scrow,f. The arm extends in the opposite direction from the shaft to arm V and carries an adjustable counter-balanoe, WV. A screw, (Z, by adjustment encounters the weight or the arm 1? and limits the range of play or vibration of the electrode 71. A light spring, K, is secured to the shaft L by a screw, f, 011 the side of the shaft opposite to arm V. An adjusting-screw, c, in contact with said spring, is used to regulate the contact-pressure of the button it on the platinum point 0. A standard or bracket, H, is secured to the base A and carries a slender spring, M. To the end of this spring is secured a small non-oxidizable or plumbago point, a, and the spring is so bent that it will follow the electrode it through its range of movement and remain always in contact therewith.

N is one binding-post of the instrument; S, the other. From N a wire, E, leads to bracket H and spring M, while another or branch wire, E,is connected to the diaphragm. The standards or supports B B are connected to the post S by wiresF and I.

The impulses or undulations are mainl y produced in the circuit including the diaphragm, and the electrodes 7t. 0 in the arm V; but the yielding nature of the contact between button it and point it contributes also to this effect. W'ith this form of instrument the circuit is not broken by loud or sudden sounds directed against the diaphragm, and a great distinctness and clean ness in the sounds reproduced is the result. The great delicacy of adjustment of which the instrument is capable adds very greatly to its efficiency and easy management. I have found ICO that its opera ion i not m r ally aff c ed by the position in which it is used.

The construction of the instrument may be greatly varied, and in one particular more especially, as I have shown in Fig. 3, in which the counterbalancing-arm P is supplanted by the extension V of arm V, carrying a second carbon-button holder, 0, beneath which is an adjustable limiting-stop, O. In this case the point a is preferably made to bear on the button h. The binding-post N is connected to the diaphragm, as before, and also, by means of a wire, E, to the support carrying the spring, to which is secured the point a.

The manner of using the instrument is well understood. It may be used either with or without an indnctioucoil and with any of the ordinary forms of receiver.

What I claim as my invention is-- nation, with the main electrodes, of an independent conducting-point of relatively small 1. In a telephonic transmitter, the combima electrically c nnected to one of the ten minals of the transmitter and in permanent yielding contact with the electrodes of the 0pposite terminals, as set forth.

2. In a telephonic transmitter, the combination,with the main electrodes, of a light independentlyspring-supported carbon point in permanent yielding contact with the vibrating carbon electrode and in electrical connection with the opposite terminal of the instrument, as set forth.

3. The combination, with the shaft L, the arm V and the electrode it carried thereby, the electrode 0, the connterbalancing-arm P, and the spring K,of the bracket H, the spring M, and contactpoint a carried thereby and bearing upon the electrode h, as described.

MOSES G. FARMER- Witnesses:

WALLAoE E. DIXON, TIMOTHY DAME. 

